I haven't finished the video yet but with how many w you missed and mentioned the sidesteps like 6:20 for instance in this case it's much better and more consistent to throw e first and then w to apply the slow first makes it way harder to dodge. In many cases it can be good to throw w then e to make it more unexpected but in situations like the one i timestamped trist obviously has to expect you going for a w. There's no way to surprise her and therefore no advantage to throwing w first.
Ieona decided that he wants to fight, and he doesn't stay under the turret. That was the losing mistake, I think. If they stay under the turret, maybe you can't end, and you need to base because of Tristana.
No offense but what elo is this? If this is high elo then what a joke because 1) your varus lost lane with a constantly roaming enemy Leona 2) Varus doesn’t know how to look at map 3) Tristana literally refused to back and just blindly attacked turrets thinking your siege wouldn’t take her nexus. I’m a masters player and I acknowledge I’m not all that great but this is definitely a really awful game for a high elo one. Your early game was abysmal too but I know we all have bad games, no shade much love broxah.